1. Field of the Invention
The present invention relates to a lubricating apparatus for a rotating shaft and, more particularly, relates to a lubricating apparatus for introducing oil into an oil passage in the rotating shaft from the outside and supplying the oil to portions where gears and like are fitted to the outer peripheral surface of the rotating shaft.
2. Description of the Related Art
The lubricating apparatus as described above, for example, have been used for lubricating portions where a speed-change gear are fitted on a speed-change shaft, in a gear-type transmission. As a system for supplying oil into the oil passage in a rotating shaft from the outside, there have been a forced-supply system utilizing an oil pump, and a natural supply system utilizing water-head differential pressure (head differential pressure) in oil. Such the forced-supply system hardly induces shortage of the amount of oil supplied to the oil passage in the rotating shaft, except in the event of failures of the oil pumps, and the like. However, such the natural supply system may induce shortage of the amount of oil supplied to the oil passage, in the event of reduction of the water-head differential pressure. Namely, within an oil chamber to which the oil passage is opened, oil is moved outwardly in the radial direction and is pressed against the inner peripheral surface of the peripheral wall of the oil chamber, due to centrifugal forces based on the rotations of the end surface of the rotating shaft and an inner ring in a bearing. When the water-head differential pressure is lower, oil hardly flows into the oil passage from the oil chamber, since oil can not overcome the centrifugal force.
As a countermeasure against shortages in the amount of oil supply, Japanese Examined Utility Model (Registration) Application Publication No. 61-12451 discloses a lubricating apparatus which is provided with an oil guide 110, as illustrated in FIG. 11. The structure of FIG. 11 will be described briefly. A speed-change shaft 102 is rotatably supported by a side wall 100 of a transmission case with a bearing 101 interposed therebetween, and the speed-change shaft 102 is provided, in its shaft center line portion, with an oil passage 104 extending in the axial direction. On the inner surface of the side wall 100, the oil guide 110 is provided such that the oil guide 110 extends from an oil receiver 103 and reaches an opening of the oil passage 104 in the speed-change shaft 102. The oil receiver 103 is supplied with oil having been scraped away by a rotating ring gear, and the oil is supplied to the oil passage 104 through the oil guide 110 due to a water-head differential pressure therein.
However, the oil guide 110 in FIG. 11 forms only the single oil flow path which extends from the oil receiver 103 and reaches the oil passage 104. Therefore, when the water-head differential pressure is lower, and there are larger centrifugal forces based on the rotation of the speed-change shaft 102, the amount of oil supplied to the oil passage 104 may be reduced.